Open almost any GEDCOM and there are tags the standard never defined: _UID, _APID, _MILT, _PRIM. The underscore is the signal. It means "the program that wrote this file made this up". The standard permits it, and every vendor does it, because the standard has no field for half of what people record.

They are not errors. They are extra data. A viewer that ignores them loses nothing structural; a viewer that reads them shows more.

The ones seen most

  • _UID. A unique identifier for a record, written by many programs (RootsMagic, Family Tree Maker, Legacy, Gramps and others). Lets a program recognize the same person across two exports even if the I-number changed.
  • _APID. Ancestry's record reference. Appears on citations in Ancestry and Family Tree Maker exports and looks like 1,1234::5678910. The middle number identifies which Ancestry record collection the fact came from. It cannot be opened from outside Ancestry, but it says where a citation originated. GED-VIEW shows the collection number.
  • _TMPLT. RootsMagic's source template. When a source is entered in RootsMagic using one of its Evidence Explained templates, the export writes the template's fields (page number, URL, film number and so on) as named pairs under _TMPLT. Most viewers discard this. GED-VIEW shows it as a small table on the source page.
  • _PRIM. Marks the primary photo for a person. Written by Family Tree Maker, Legacy and others.
  • _MILT. Family Tree Maker's military service event.
  • _MREL and _FREL. Family Tree Maker's relationship of a child to mother and father: natural, adopted, step.
  • _MARNM. Married name, written by several programs and websites.
  • _UPD. MyHeritage's last-updated timestamp.
  • _SDATE. RootsMagic's sort date, for ordering events with vague dates.
  • _PHOTO, _WEBTAG, _COLOR, _TAG. Various programs' extras for photos, links, colour coding and flags.

What GED-VIEW does with them

Reads the ones it knows and shows them where they belong: _TMPLT on the source page, _APID as a collection reference, _PRIM to pick the profile photo, _MREL and _FREL on the relationship. Anything it does not know is kept and counted, and there is a section in GED-VIEW that lists every unrecognized tag in the file with how often it appears and sample values, so nothing is silently lost. If a tag from your program appears there and should be displayed somewhere, the support form is the place to say so.

What GEDCOM 7 did about this

7 added a way to declare extensions properly in the header, and a standard tag (EXID) for external identifiers like Ancestry's, so future files should need fewer underscores. The old ones will be around for years regardless.

Next

Open a file and look at the unrecognized tags section. Whatever is there is the program's extras, not a fault.